The present invention relates to a new and distinct cultivar of Heuchera and given the cultivar name of ‘TNHEULS’. Heuchera is in the family Saxifragaceae. Heuchera ‘TNHEULS’ originated as a controlled cross using Heuchera B447-3′, a proprietary, unpatented, unnamed plant as the seed parent, and Heuchera ‘B446-1’, a proprietary, unpatented, unnamed plant as the pollen parent. These parents are part of a breeding plan to produce a sun tolerant yellow to lime foliage Heuchera. 
Compared to the seed parent, Heuchera ‘B447-3’, the new cultivar has a larger crown and habit.
Compared to the pollen parent, Heuchera ‘B446-1’, the new cultivar has shorter inflorescences and a larger habit.
Compared to Heuchera ‘Lemon Chiffon’, U.S. Plant Pat. No. 19,033, the new cultivar has improved sun tolerance, thicker leaves, and larger flowers that are white rather than light coral pink.
This new Heuchera is uniquely distinguished by:                1. better sun tolerance compared to other known yellow foliage cultivars,        2. white flowers on medium short spikes,        3. full crown of lime-green spring leaves that turn to yellow in the sun,        4. medium-small mounding habit, and        5. excellent vigor.        
This new cultivar has been reproduced only by asexual propagation (tip cuttings and micropropagation using growing tips). Each of the progeny exhibits identical characteristics to the original plant. Asexual propagation by cuttings and tissue culture using standard micropropagation techniques with terminal and lateral shoots, done in Canby, Oreg., shows that the foregoing characteristics and distinctions come true to form and are established and transmitted through succeeding propagations. The present invention has not been evaluated under all possible environmental conditions. The phenotype may change with variations in environment without a change in the genotype of the plant.